The present invention relates to a silicon wafer holding container, specifically designed for vacuum storing and/or shipping silicon wafers and having particularly useful characteristics.
As is known, silicon wafers or slices, used for making IC's, are thinned, at the end of the processing thereof, to a thickness of 300 microns, electrically tested and then sent to the assembling operations. Frequently these steps are carried out after a long time from the processing and testing operations, and, accordingly, the silicon wafers must be stored for a given time; moreover the assembling place is frequently very spaced from the place of manufacture and, because of this reason, the silicon wafers must be shipped in a very safe condition.
In both cases there are necessary wafer holding elements or containers which must meet some precise requirements, that is:
(a) they must be of the vacuum type, in order to prevent the wafer from absorbing moisture; PA1 (b) they must be mechanically strong and protective, for properly protecting the thin and brittle silicon wafers; PA1 (c) they must have minimum weight and size, to reduce to a minimum the shipping cost; PA1 (d) they must be made of inert materials, in order to not contaminate the wafers, and must be constructed so as to not contact, or contact in a minimum degree, the two faces of the silicon wafers, in order not to contaminate them; PA1 (e) they must not impose electrostatic charges on the wafers.
There are commercially available some wafer containers which, on the other hand, do not possess all of the above stated requirements; for example these known containers release metal impurities (such as sodium, potassium), thereby damaging the wafers, or contact the silicon wafers in several points, thereby preventing them from being vacuum packaged, or have high size and cost as well as can be hardly vacuum packaged in an automatized way.
An object of the present invention is to provide a wafer container which may be easily vacuum packaged, which is capable of properly mechanically protecting the thin silicon wafers, which is provided with suitable antistatic characteristics, which does not contaminate the silicon wafers and which, moreover is capable of also storing partial or not complete silicon wafers.
This and other objects of the invention will become more apparent to those skilled in the art from the following description.